An 18 oz jar of peanut butter cost $2.19. a 48 oz jar of peanut butter sells for $4.39. which size jar is the better buy? why? will give 15 points.

Ok, so we need to find the price per ounce.  If we take 2.19 and divide it by 18 that gives us 0.12 per ounce of peanut butter.  If we take 4.39 and divide it by 48 that gives us 0.09.  So we know the cheapest option is the 48 ounce jar.  Also, teachers love it if you include something like "However, if you don't need 48 ounces of peanut butter, the other jar is only 0.03 more per ounce."